Recently, IT has been fundamental to business and taken on a growing importance. Thus, the effect of a system down is enormous. In the case of finance industry, it is reported that the loss due to the system down reaches several million dollars by hour, for example. In such an environment, a disaster recovery (hereinafter referred to as DR) to backup data to a remote site in order to continue the business even if any disaster occurs has come under the spotlight.
As a method to achieve the transfer between sites in the DR system, a method using a high performance storage having a remote copy function has gotten a lot of attention. The advantage of the method using the remote copy is that the transfer between sites can be achieved without consuming the resource of the server.
According to the circumstance of the legal control in response to terrorism and wide area disasters, even the DR system using the remote copy is required to accomplish the following objects at the same time: (1) Business can be restarted at a sub-site without the loss of data even in the event of a disaster; and (2) The online performance of the main site can be maintained even if the sub-site is located at the remote site away from the main site more than several hundred km in order to cope with the case of a wide area disaster.
The DR system is introduced mainly into financial industry and large companies at present. However, it will be necessary for medium and small companies to introduce the DR system in order to prevent risks and grade up the companies for the future. In order to extend the applicable scope of the DR system to medium and small companies, it is important that the cost of the DR system is reduced in addition to the achievement of the above-described two objects. Meanwhile, the exclusive line is mostly used for the present DR system from the viewpoint of reliability and security. Since enormous money is required to construct and maintain the broadband exclusive line, the line cost must be reduced in order to reduce the cost of the DR system.
As a method to solve the above-described problem, a DR method in which only log files of a database management system (hereinafter referred to as DBMS) are transferred through a remote copy operation and the file of a database (hereinafter referred to as DB) is recovered from the logs in the sub-site has attracted a log of attention. Since it is not necessary to transfer a DB file in this method, it is possible to significantly reduce the line cost. Additionally, in the DR method in which logs are transferred, the speed-up of the switching (the failover) in the event of a disaster and the intentional switching and the operation manageability are required nowadays.
As a method of transferring a log file through a remote copy operation and recovering a DB file (DB volume: hereinafter the volume is referred to as VOL) in the sub-site, the conventional method 1 (SANRISE Solution Suite with Oracle ) and the conventional method 2 (US Patent No. 5640561) are known, for example.
<Conventional Method 1>
The conventional method 1 is shown in FIG. 15. FIG. 15 is a diagram showing an example of the configuration of a system to which the conventional method 1 is applied. In FIG. 15, reference numeral 101 is a DBMS in a server 100 of a main site, 1400 is a DBMS in a server of a sub-site, 120 is a storage of the main site, 130 is a storage of the sub-site, 128 and 138 are log VOLs, 129 and 139 are DB VOLs, 1401 and 1411 are archive log VOLs and 1402 is a network, respectively. In addition, reference numerals 1403, 1404, 1405, 1406 and 1407 denote the processing routes of a remote copy operation, an inter-server transfer, a log reading, a log application, and an archiving, respectively.
Generally, in the log file (log VOL) on which the log which is the update difference to the DB is recorded, the generation management of a plurality of log files is performed and a new log is additionally recorded while switching at the timing of, for example, capacity shortage. At this time, since the log file is repeatedly overwritten, an archive log file (archive log VOL) is created in order to save the content of the original log file.
In the method of FIG. 15, the log is transferred through a remote copy operation and an archive log is transferred between the servers. The archive log is received at a standby DBMS of the computer in the sub-site and the received archive log is applied to recover the DB (DB VOL).
<Conventional method 2>
The conventional method 2 is shown in FIG. 16. FIG. 16 is a diagram showing an example of the configuration of a system to which the conventional method 2 is applied. In FIG. 16, a reference numeral 1600 is a processing route representing an archiving, and the same components as those in FIG. 15 are denoted by the same numerals and symbols as those in FIG. 15.
Only logs are transferred through the remote copy operation in the method of FIG. 16. In the sub-site, the creation of an archive log file in the main site is monitored. When it is detected that the archive log file is created, the sub-site independently creates an archive log file, and then the created archive log file is applied to update the DB.